1. Technical Field
This invention relates to an image forming apparatus and method, and in particular to an image forming apparatus and method capable of weakening an electric field generated under a printing head.
2. Related Art
As an image forming apparatus, such as a printer, a facsimile machine, a copier, a plotter, a multifunctional machine combining these capabilities, etc., an ink-jet printer that employs a droplet ejecting-type printing system with a droplet discharging head that ejects droplet is known.
In such an image forming apparatus, a droplet having landed on a printing medium takes a long time to dry and form an image thereon. For this reason, the printing medium is conveyed with its image forming surface distanced from (i.e., not contacting) a sheet conveyor until the droplet on the printing medium dries.
Certain known conveying systems convey the printing medium using electrostatic force generated in a sheet conveyor to attract the printing medium. However, the electric potential at the sheet conveyor cannot be completely eliminated under a printing head acting as an image forming device because the electric charge previously given to the sheet conveyor remains. As a result, an ink mist readily refluxes to the printing head due to the electric field.
Moreover, a surface electric potential of the sheet at a position in a conveyance path opposed to a surface potential sensor is different from that under the printing head especially in low-temperature or low-humidity environments, in which the electrical resistance of the sheet generally increases, making it difficult to negate the electric field.